The present invention relates to a semiconductor device, for use in information communication equipment and office electronic equipment, applicable to high density packaging, containing a semiconductor integrated circuit unit and including wires and the like to be connected with external terminals, and a method for manufacturing the semiconductor device.
In accordance with recent development of compact and high level function electronic equipment, a semiconductor device including a semiconductor integrated circuit unit is also required of compactness, high packaging density and high speed in packaging work. For example, as memory packages, an LOC (lead on chip), a SON (small outline non-lead), a xcexcBGA (micro-ball grid array) using a TAB tape (disclosed in National Publication of translated version No. 06-504408) and the like have been developed.
Now, a conventional semiconductor device designated as xcexcBGA and a method for manufacturing the device will be described with reference to drawings.
FIG. 10 is a sectional view of the conventional semiconductor device designated as xcexcBGA. In FIG. 10, a reference numeral 101 denotes a semiconductor chip including semiconductor elements, a reference numeral 102 denotes a wiring circuit sheet of flexible sheet formed on the semiconductor chip 101, a reference numeral 103 denotes a flexible low elasticity material disposed between the semiconductor chip 101 and the wiring circuit sheet 102, a reference numeral 104 denotes a partial lead corresponding to a part of a wiring layer, a reference numeral 105 denotes an element electrode electrically connected with the semiconductor element included in the semiconductor chip 101, and a reference numeral 106 denotes an electrode formed on the surface of the wiring circuit sheet 102 for attaining electric connection with an external device.
As is shown in FIG. 10, in the conventional semiconductor device designated as xcexcBGA, the wiring circuit sheet 102 is formed on the semiconductor chip 101 with the low elasticity material 103 sandwiched therebetween, and the element electrode 105 on the semiconductor chip 101 is electrically connected with the electrode 106 on the wiring circuit sheet 102 through the partial lead 104.
Next, the method for manufacturing the aforementioned conventional semiconductor device will be described with reference to the same drawing.
First, the wiring circuit sheet 102 in the shape of flexible sheet is adhered onto the semiconductor chip 101 with the low elasticity material 103 sandwiched therebetween. The wiring circuit sheet 102 includes a wiring pattern therein, the electrode 106 to be connected with the wiring pattern is formed on the wiring circuit sheet 102, and the partial lead 104 extends from the electrode 106. In this case, the low elasticity material 103 is an insulating material having an adhesive function.
Next, the partial lead 104 and the element electrode 105 are electrically connected with each other by using a conventional thermo compression bonding technique generally used in xe2x80x9cTABxe2x80x9d (tape automated bonding) or an ultrasonic bonding technique. In this manner, the semiconductor device is manufactured.
Specifically, owing to the aforementioned structure of the semiconductor device, the semiconductor device can be electrically connected with external equipment through a large number of electrodes 106 two-dimensionally formed on the wiring circuit sheet 102, while suppressing stress. Accordingly, information communication equipment, office electronic equipment and the like can be downsized.
The aforementioned conventional semiconductor device has, however, the following problems:
First, in the conventional semiconductor device, it is necessary to previously fabricate the wiring circuit sheet 102, which increases the number of manufacturing processes. Also, the wiring circuit sheet 102 itself is expensive. Moreover, in order to adhere the wiring circuit sheet 102 onto the semiconductor chip 101 with the low elasticity material 103 sandwiched therebetween, it is necessary to provide a high performance placement machine, which increases the equipment cost. As a result, the manufacturing cost for the semiconductor device is increased as a whole.
Secondly, in connecting the element electrode 105 with the partial lead 104 extending from the wiring circuit sheet 102, in particular when a fine line is used for the connection, the width and the thickness of the partial lead 104 are decreased, and hence the shape of the partial lead 104 becomes unstable, resulting in making the connection with the element electrode 105 difficult. Accordingly, the manufacturing cost is increased as well as the reliability of the connection is poor.
Thirdly, owing to this structure, such a semiconductor device cannot be manufactured until the semiconductor chip 101 is cut off from a wafer. Therefore, the semiconductor device is poor in rapidness in the manufacture, and cannot be tested in the state of a wafer. This is a serious obstacle to reduction of the manufacturing cost of the semiconductor device.
The present invention was devised to overcome the aforementioned conventional problems, and the object is providing a semiconductor device with high reliability, high packaging density and low cost that can be fabricated at wafer level up to a state close to the ultimate step of the manufacture, and a method for manufacturing the semiconductor device.
In order to achieve the aforementioned object, the following semiconductor device and method for manufacturing a semiconductor device are herein disclosed.
The basic semiconductor device of this invention comprises a semiconductor substrate including semiconductor elements; element electrodes arranged on a main surface of the semiconductor substrate and electrically connected with the semiconductor elements; an elastic material layer formed on the main surface of the semiconductor substrate from an insulating elastic material; an opening formed by partially removing the elastic material layer for exposing at least the element electrodes on the semiconductor substrate; a metal wiring layer continuously formed to stretch from the element electrodes over the elastic material layer; and external electrodes formed as a part of the metal wiring layer on the elastic material layer for electrical connection with external equipment.
In this manner, the external electrodes of the metal wiring layer are formed on the elastic material layer. Therefore, in mounting the semiconductor device on a mother board, stress applied to a connection part due to a difference in the coefficient of thermal expansion between the mother board and the semiconductor device can be absorbed by the elasticity of the elastic material layer. Thus, a semiconductor device having an improved function to relax stress can be realized.
Furthermore, since the metal wiring layer connected with the element electrodes is integrated with the external electrodes, the metal wiring layer can be formed by patterning a metal film deposited on the semiconductor substrate. Accordingly, there is no need to provide a wiring circuit sheet and equipment for the wiring circuit sheet as in the aforementioned conventional semiconductor device. Also in the manufacture, there is no need to conduct a process for connecting a partial lead with an element electrode through thermo bonding as in the procedures for the conventional semiconductor device. As a result, the manufacturing equipment and the number of manufacturing procedures can be reduced, and difficulty in the connection can be avoided. Thus, the manufacturing cost can be reduced.
In addition, the manufacturing procedures can be simplified because the metal wiring layer can be formed even when the semiconductor substrate is in the state of a wafer.
In the semiconductor device, the semiconductor substrate can be in the state of a wafer or in the state of a chip cut off from a wafer.
In the semiconductor device, the elastic material layer preferably has a wedged section inclined to the surface of the semiconductor substrate or a round-cornered section in an end portion thereof in the vicinity of the opening.
When the elastic material layer has any of these sections, stress can be avoided from being collectively applied to a part of the metal wiring layer, and hence, disconnection of the metal wiring layer and the like can be prevented, resulting in improving the reliability of the semiconductor device.
The semiconductor device preferably further comprises a protecting film formed to cover the metal wiring layer and having a property to repel a conductive material; and openings each formed through the protecting film for exposing at least a part of each of the external electrodes of the metal wiring layer, and an external electrode terminal is preferably formed at least on a part of each of the external electrodes exposed in the openings of the protecting film.
In this manner, while keeping normal connection between the metal wiring layer and wiring electrodes on a mother board having no electric short-circuit, the semiconductor device can be satisfactorily mounted on the mother board.
In the semiconductor device, the external electrode terminal can be made from a metal ball formed to be in contact with each of the external electrodes or a conductive projection formed to be in contact with each of the external electrodes.
Alternatively, at least a part of each of the external electrodes exposed in the openings of the protecting film can also function as the external electrode terminal.
The semiconductor device can further comprise a passivation film for protecting the semiconductor elements formed on the semiconductor substrate and having openings above the element electrodes, and the elastic material layer can be formed on the passivation film.
In this manner, a semiconductor device with higher reliability can be obtained.
The basic method for manufacturing a semiconductor device of this invention comprises a first step of forming an elastic material layer from an insulating material on a semiconductor substrate including semiconductor elements and element electrodes electrically connected with the semiconductor elements; a second step of forming an opening in the elastic material layer for exposing the element electrodes by selectively removing the elastic material layer in areas above the element electrodes; and a third step of forming, on the substrate bearing the elastic material layer and the opening, a metal wiring layer stretching from the element electrodes exposed in the opening over the elastic material layer, a part of the metal wiring layer functioning as an external electrode for electric connection with external equipment.
In this method, the metal wiring layer connected with the element electrodes can be formed integrally with the external electrodes by patterning a metal film deposited on the semiconductor substrate. Accordingly, there is no need to provide a wiring circuit sheet and equipment for the wiring circuit sheet as in the conventional semiconductor device. In addition, there is no need to conduct a process for connecting the partial lead with the element electrode as in the manufacturing procedures for the conventional semiconductor device. Accordingly, the manufacturing equipment and the number of the manufacturing procedures can be reduced. Furthermore, since the metal wiring layer can be electrically connected with the element electrodes merely by forming the metal wiring layer on the element electrodes, difficulty as in the connection between the partial lead and the element electrode in the conventional semiconductor device can be avoided. As a result, the basic semiconductor device of the invention can be easily realized with the manufacturing cost reduced.
In the basic method for manufacturing a semiconductor device, the first through third steps are preferably conducted on the semiconductor substrate in the state of a wafer, and the method preferably further comprises, after the third step, a step of dividing the wafer into semiconductor chips.
In this manner, the elastic material layer, the metal wiring layer and the like can be formed in a large number of chip areas with retaining the semiconductor substrate in the state of a wafer before dividing into chips, and hence, the manufacturing cost can be largely reduced.
The basic method for manufacturing a semiconductor device can further comprise, before the first step, a step of dividing a wafer into semiconductor chips, and the first through third steps can be conducted on the semiconductor substrate in the state of a chip.
In the method for manufacturing a semiconductor device, in the second step, the elastic material layer is preferably formed to have a wedged section inclined to a surface of the semiconductor substrate in an end portion thereof in the vicinity of the opening.
Thus, a highly reliable metal wiring layer hardly suffering disconnection can be formed.
The method for manufacturing a semiconductor device preferably further comprises, after the third step, a step of forming a protecting film for covering the metal wiring layer excluding at least a part of the external electrodes.
Thus, the external electrodes of the semiconductor device can be easily and rapidly connected with wires of a mother board by using a connecting member such as solder.
The method for manufacturing a semiconductor device preferably further comprises a step of providing a metal ball on each of the external electrodes of the metal wiring layer.
Thus, the semiconductor device can be very rapidly mounted on a mother board by using the metal balls.
The basic method for manufacturing a semiconductor device can further comprises, after the third step, a step of testing the semiconductor device by installing a testing board including terminals electrically connectable with the external electrodes above the semiconductor substrate.
Thus, the semiconductor device can be tested while absorbing, by the elastic material layer, stress applied to the metal wiring layer through the external electrodes during the test.